The present invention relates to select call receivers (pagers) used to receive various types of messages. Modern pagers are categorized by the method in which information is transferred to them and the way in which the information is provided to the user of the pager. For example, pagers have be categorized as "tone", "voice", "numeric", and "alpha-numeric" types.
Each category of pager has certain advantages and disadvantages which result from trade-offs between the cost of service, the cost of the pager itself, and level of information provided to the user upon receipt of a message. In a tone pager, for example, the pager produces an audible beep tone upon receipt of a message. A user of a tone pager will have established an understanding with the person who initiates a message that a certain action will occur as a result of receiving the message. The user may call a certain telephone number, for example.
Pager users have a need and a desire to receive more detailed messages from their pager in order to make the pager more flexible in its function and easier to use. In an alpha-numeric pager, the message received can be very detailed and easy to understand by virtue of the large choice of characters that can be transmitted and displayed in each message. There is a trade-off associated with these types of pagers in that the person initiating a message must communicate the details of the message to the paging carrier, who provides the paging service. For an alpha-numeric message, typically the person who initiates the message places a telephone call to the paging carrier and verbally states the message which is then entered by an operator at the paging carrier's office into a paging terminal for subsequent transmission to the desired pager. This procedure is more expensive than other categories of service because of the requirement to convert a verbal message into a digital form which can be transmitted to the pager. Furthermore, the quantity of characters transmitted is large, using more available transmitter air time. In paging systems with large numbers of users, this can limit the quantity of users who can share a system and delay transmission of messages due to a backlog of messages to be sent.
Numeric pagers strike an acceptable balance between the quantity of information presented in a message and the resources necessary to send a message. It is common for a message to be initiated by placing a telephone call to an automated paging terminal. Then the pager identity and numeric message information are entered using the key pad on a telephone. The numeric message information is subsequently transmitted to the pager and displayed on a display in the pager. It is common that the numeric information is a telephone number. The user, upon viewing the received message, places a telephone call to the number displayed in response to the message. Because of the foregoing, numeric pagers have become popular and are the most widely used type of pager in the United States.
Numeric pagers have been adapted to provide a greater quantity of information without significantly increasing the number of digits transmitted in a single message. For example, numeric pagers are available which have alphanumeric displays that display alpha-numeric messages in response to numeric codes they receive. Such a pager may have a memory which links a two digit numeric value and a canned alpha-numeric message. "00" might be linked with "URGENT", for example. Being such, a message can be transmitted with a "00" in addition to the usual numeric message. Upon receipt of the message, the pager would parse the "00" portion of the message from the whole message received, and recall the canned message "URGENT" linked therewith. Then, the pager would display "URGENT" on the first page of the display and the numeric message on the second page of the display. In this way, the user is clearly alerted that the message is urgent with the addition of only two numeric digits in the originally transmitted message. It is known that pagers are programmed with a variety of standard canned messages which are likely to be used from time to time. Each of these messages may have its own unique numeric identifier. The unique numeric identifier is called a message tag identifier or simply a tag. The tags can be comprised of one or more numeric digits and two digits is commonly used.
Canned messages are useful, but, they do not meet the user's needs in every situation. Often times, it is desirable to have a message which is customized to a particular need. A user might want to have the name of an associate available as a canned message, for example. Since canned messages are typically preprogrammed either at the time of manufacture or when the pager is initially programmed by the service provider, it is difficult for an end user to change or upgrade the list of canned messages. If a user desires to make a change in the list of canned message, the user is required to return the pager to the service provider to have a memory programming change made. Another limitation of canned messages is the two digit numeric code correlated to each message. It can be difficult and confusing for people who initiate messages to a pager users to remember which codes solicit which canned messages.
There may be many creative ways to improve the foregoing paging environment. Certainly in other communications media, many improved communications schemes could be envisioned. However, with pagers, there are certain constraints which limit the options for improving the communications scheme. The signaling protocol, the existing hardware infrastructure, and the limits of a telephone keypad as a data entry terminal define these limits. The signaling protocol which is widely used in paging is known as the POCSAG signaling protocol. Any improvements must be made under the constraints of the POCSAG protocol.
FIG. 1 illustrates a typical numeric paging system in the prior art. An automated paging terminal 1 is coupled to a broadcast antenna 2 which radiates radio waves that are received by pagers 3, 4, 5, or more. Messages are initiated by accessing a telephone 6, 7, 8 and placing a telephone call, via the public switched telephone network 9, to the paging terminal 1. Upon accessing the paging terminal, a PIN (Personal Identification Number) is entered which correlates to a capcode within the paging terminal thereby defining the particular pager which is intended to receive the message. Next, a numeric message is entered on the telephone keypad which is to be displayed by the pager. Having received a telephone call specifying the PIN of a particular pager and a numeric message, the paging terminal broadcast the capcode associated with the PIN together with the numeric message. Any pager with the specified capcode enabled will receive and decode the message.
The POCSAG protocol defines the encoding, transmission and decoding scheme used in many pagers. Each POCSAG transmission begins with a preamble. The preamble is a sequence of bit reversals used to alert the pagers of an upcoming broadcast. Following the preamble is a plurality of data batches, each of which begins with a synchronization code word that defines the beginning of each batch. Each batch contains eight frames of data. Each frame comprises two 32 bit code words which may contain an address code word or a message code word. Address code word data contains a capcode and is used to designate which pager is to receive the data, and, message code word data is the data which contains the message information.
Within each pager is stored one or more capcodes, in a capcode memory, which are unique codes that are compared with the address code word data in a broadcast data frame to determine if a particular message is intended for a particular pager. The use of address code word data and capcodes are well known to those skilled in the art and will not be discussed further.
Message code word data are received and decoded by a pager when the address code word and capcode correspond. Message code word data comprises 32 bits of information. The first bit is the address/message flag and is set to "1", by definition, for all message code word data. The next 20 bits of data contain the message, or a portion of the message, intended for the pager. The next 10 bits are used for error detection and correction, and the final bit is used for further error detection by even parity. If a message exceeds the 20 bit message data capacity of a single message code word frame, data from additional frames are concatenated with data from the initial frame to provide the necessary data capacity. The forgoing message code word data structure is well known to those skilled in the art and will not be discussed further.
The present invention sets forth an apparatus for adding flexibility and simplicity to the use of canned messages. This invention benefits people originating pages by simplifying the message input procedure, benefits the paging carrier by allowing more comprehensive messages to be communicated with little data overhead and no modifications to the infrastructure equipment, and benefits the pager user by adding the flexibility of programmable canned messages and improved information availability.